The World in Three Dimensions…

There was a time when people argued that theatrical (even home) sound has long been three dimensional. Maybe there are still some that make that claim. With the rise of binaural audio, Dolby Atmos and Auro 3D, sound actually is entering the third dimension. This is just a small semantic argument. Surround sound, in its traditional 5.1 and 7.1 formats, wasn’t technically three dimensional. It was still a two dimensional plane, but that plane was perpendicular to the screen. In a way, it made the viewing experience three dimensional. Here we had the 2D screen on the vertical plane, and the 2D sound on the horizontal. The world of the film could extend away from the screen to envelop the viewer. As the presence of three dimensional image grows in our media consumption experiences, it’s become even more important to make good use of the surround technology at our disposal. The visual experience is now as immersive as the aural.

With that fact in mind, we turn our focus this month to the topic of “Surround.”

Next month’s featured topic will be “Silence.” As always, we want your guest contributions. If you have an idea you’d like to explore, or something you want to put in front of the community, whether it be as part of our monthly topic or something further afield, please contact us. Email Shaun, or use our contact form to get the ball rolling.

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5 Comments

agree with you. The ‘perceptive’ third dimension is distance, still missing in conventional surround tech. The German audio labs from IOSONO made it – it is called PROXIMITY. Pinpointing sound sources aligned in respect of direction and distance with its positions in the real gameplay. Works with speakers and headphones, too.

I believe that conventional surround sound is even less than 2 dimensional in some respects. The perpendicular sound plane you mention actually stops at the vertical screen plane, as that’s where the speakers are. No sound can appear to come from ‘behind’ the screen. This phenomenon is particularly apparent in HFR 3D, since we can visually look beyond the screen plane into the very far distance. Current immersive sound technology – including that of Auro and Atmos – doesn’t address this screen boundary problem at all. Binaural sound will preserve the depth element, but that of course is problematic in a cinema environment.

You raise some interesting points, Peter, but I’ll play devil’s advocate here. I’ll grant you that this is somewhat dependent on listening position, but I have yet to hear a binaural example of distance in the frontal plane that cannot be recreated with a more “conventional” playback systems. If you really want to get semantic in the discussion, all theatrical sound is emitted from behind the screen to begin with (…though, obviously, not exactly your point). There’s also the issue that effective binaural playback is highly dependent on how well the HRTFs calculations used align with the individual listener. I myself have listened to binaural presentations that work perfectly for others, while presenting issues with consistency of image for me. From my perspective, creating depth in non-binaural systems is not terribly difficult.

I’ve done extensive work with binaural and I disagree that true sonic depth can be created with conventional and existing cinema sound methods. You certainly can create a facsimile of depth but there’s a simple physics problem that you can’t overcome: a sound that is further away from the screen plane interacts with everything else that’s further away from the screen plane to tell your brain where it sits in space. This is extremely easy to demonstrate (I’m surprised that you say you have yet to hear an example of it, in fact): set up a camera on a quiet path among some buildings and get someone wearing hard shoes to walk away from you. With a binaural recording you can plainly hear the person walking off into the distance. They _sound_ distant. Now attempt to emulate that effect with a mono recording, volume control and any verbs and delays you choose (since this is what you’d do in a film mix). You’ll never match it. You might get something that sounds acceptable – in fact, in this day & age I should hope you could* – but the binaural recording preserves complex elements of the real environment that your ears and brain can very accurately place – and not just laterally, but vertically as well. This situation becomes acute when you’re dealing with multiple sounds. Right now, as I sit writing, I can hear a very complex layering of sound outside – birds in a tree close, a more distant bird calling, a dog barking, traffic and the local highschool PA playing music. All these sounds are clearly layered in their appropriate distance. If I close my eyes I can tell you exactly where they are in respect to one another in terms of distance. No-one, no matter how clever, could emulate this complexity to simulate the reality sufficiently. But a single, simple binaural recording would capture it all.

You quite correctly point out the wealth of problems that binaural presents, and I’m not suggesting that it would be a desirable or even plausible solution for a cinema environment, only that it points out the failing of conventional sound models to provide accurate representation for sound beyond the screen plane (and yes, I am aware that the speakers sit behind the screen – a full 3 feet of awesome extra depth if you’re lucky :p)

If you get a chance, try and catch a screening of The Hobbit in HFR and 3D (I guess this might be tricky now, until the next one comes out). It vividly demonstrates the issue. The mix on this film is excellent – there’s nothing to fault as a standard 2D cinema mix. I’ve watched it on Blu-ray in my studio and it’s a great job from all concerned. In HFR 3D, however, the sound does a weird thing – it becomes flat and featureless. It’s like the detail is sucked out. Complex scenes feel like washes of sound with effects poking out in a very ugly way. It took me three viewings to figure out why – most of the visual depth is beyond the screen plane, and the sound doesn’t stick with it. It’s acceptable in 2D because we’re used to the convention, but as 3D image approaches very realistic levels, your ears and brain are trying to deal with a cognitive dissonance.

(*I’ll make a slight caveat here: convolution verbs will be hugely helpful, I accept. The thing is, a stereo convolution verb is actually providing aspects of binaurality, due to the nature of the convolution recording process).

Yes, there are certainly details that can’t be emulated outside of binaural recording, but the argument that the plane cannot extend beyond the screen without it feels overly assertive to me. I also feel the issues with HFR 3D has little to do with the sound presentation. It’s a fundamental shift in composition of the visuals, and the process of cinematography needs time to adapt and learn to use it to best effect.